While running, a person dissipates about 0.6 J of mechanical energy per step per kilogram of body mass. If a 60-kg person runs with a power of 70 Watts during a race, how fast is the person running? Assume a running step is 1.5 m long.
[Ques. 2] A simple pendulum, 2.0 m in length, is released from rest when the support string is at an angle of 25 from the vertical. What is the speed of the suspended mass at the bottom of the swing?
[Ques. 3] A 70-kg high jumper leaves the ground with a vertical velocity of 6.0 m/s. How high can he jump?
[Ques. 4] A surprising demonstration involves dropping an egg from a third-floor window to land on a foam-rubber pad 2 in (5 cm) thick without breaking. If a 56-gram egg falls 12 m, and the foam pad stops the egg in 6.25 ms, by how much is the pad compressed?
[Ques. 5] A rain cloud contains 2.66 107 kg of water vapor. How long would it take for a 2.0 kW pump to lift the same amount of water to an altitude of 2 000 m?
[Ques. 6] Starting from rest at t = 0, a 5.0-kg block is pulled across a horizontal surface by a constant horizontal force having a magnitude of 12 N. If the coefficient of friction between the block and the surface is 0.20, at what rate is the 12-N force doing work at t = 5.0 s?
a. 0.13 kW
b. 0.14 kW
c. 0.12 kW
d. 26 W
e. 12 W
[Ques. 7] A 3.0-kg block is on a horizontal surface. The block is at rest when, at t = 0, a force (magnitude P = 12 N) acting parallel to the surface is applied to the block causing it to accelerate. The coefficient of kinetic friction between the block and the surface is 0.20 . At what rate is the force P doing work on the block at t = 2.0 s?
a. 54 W
b. 49 W
c. 44 W
d. 59 W
e. 24 W
[Ques. 8] A 1.6-kg block slides down a plane (inclined at 25 with the horizontal) at a constant speed of 2.0 m/s. At what rate is the frictional force changing the mechanical energy of the block?
a. +28 W
b. +13 W
c. 13 W
d. 28 W
e. +6.5 W
[Ques. 9] A 3.0-kg block is on a frictionless horizontal surface. The block is at rest when, at t = 0, a force (magnitude P = 2.0 N) acting at an angle of 22 above the horizontal is applied to the block. At what rate is the force P doing work at t = 2.0 s?
a. 2.3 W
b. 2.0 W
c. 1.4 W
d. 1.7 W
e. 1.2 W
[Ques. 10] The speed of a 4.0-kg object is given by v = (2t) m/s, where t is in s. At what rate is the resultant force on this object doing work at t = 1 s?
a. 48 W
b. 40 W
c. 32 W
d. 56 W
e. 16 W
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